ABSTRACT
For the constant velocity 15-degree space-frequency ( )
time migration algorithm, the parabolic approximation of
the exact one-way wave equation causes undermigration,
and the Crank-Nicolson numerical method that is used to solve the
diffraction equation causes overmigration.
However, the modified wave equation that the numerical
solution actually satisfies for the diffraction equation
shows that the trace spacing interval plays a larger role than
the depth step size of downward continuation
in determining the accuracy of the numerical solution.
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